Randomized trials show consistent benefits among patients who engage in regular physical activity as part of a structured cardiac rehabilitation program. However, failure to maintain even moderate levels of physical activity following rehabilitation has been a fundamental problem. This research is based on the wellness motivation theory, which consists of three dimensions: contextual influences, behavioral change processes and action. The action of interest is physical activity. The purposes of the study are: 1) to determine which variables in the theory are significant predictors of physical activity, including state of activity maintenance, exertion level, and physical fitness, over time, in individuals with diagnosed CHD who have completed a program of cardiac rehabilitation; and 2) to develop and evaluate the strength, effect size and acceptability of an intervention to enhance motivation in the achievement of physical activity. The proposed study will be conducted in two phases. In Phase I, a longitudinal fixed cohort of 312 adults will be sampled following graduation from cardiac rehabilitation. The dependent variables and predictor variables indexing contextual influences, behavioral change processes and physical activity will be measured at three periods: 1) 2 weeks following completion of outpatient cardiac rehabilitation (T1); 2) 3 months following completion of a cardiac rehabilitation (T2); and 3) 6 months following completion of cardiac rehabilitation program (T3). Hierarchical logistic regression will be used to determine which contextual and behavioral change process variables are significant predictors of state of physical activity maintenance. Structural equation modeling will be used to examine the relative impact of key variables in the theory on exertion level and physical fitness. The intervention to be designed to Phase II will include variables found to be predictive of state of activity maintenance, exertion level and physical fitness. Intervention strength will be evaluated through expert review of the intervention treatment manual and audiotape transcriptions of randomly selected intervention sessions. Intervention components will be retained if they are evaluated as at greater than average strength for enhancing motivation for physical activity. Effect size will be determined by changes in participant mean scores on physical activity measures from baseline to post-intervention (T1-T2). Intervention acceptability will be assessed through participant evaluations of the effectiveness of each component and audiotape transcriptions of exit interviews.